Insulator and method of making it



Patented Mar. 2, 1937 PATENT OFFICE INSULATOR AND METHOD 0F MAKING IT Clarence H. Dibble, Corning, N. Y., assignor to Corning Glass Works, Corning poration of New York N. Y., a cor- Application July 28, 1933, Serial No. 682,682

l Claim.

This invention relates to insulators and more particularly to a method of preventing the adhesion of the dielectric body to the metal parts of an insulator. In the manufacture of insulators of any type employing metal parts, particularly suspension insulators, it is customary to ailx the metal parts to the dielectric parts by means of molten alloy. When it is necessary to heat the dielectric part, as for instance in the manufacture of glass insulators prior to introducing the alloy, there frequently occurs a wetting of the glass by the alloy which results in the adhesion of the alloy to the glass. Such adhesion is objectionable because due to the difference of the coeiilcient oi expansion of the glass and the a1- loy, strain is set up between the two and breakage of the glass frequently occurs.

In order to prevent the adhesion of the alloy to the glass, oil has been used on the surface of the vglass but due to its volatilization and gassing under heat, it was found that porous castings of the alloy were formed with a resulting lack of strength ofthe assembled unit.

The object of the present invention is to prevent the adhesion of molten alloy to dielectric materials, particularly glass.

Another object is to produce perfect castings of the alloy and hence improve the strength of the completed insulators.

The above and other objects may be accomplished by employing my invention which embodies among its features preventing the adhesion of the dielectric of an insulator to the alloy by which metal parts are attached to it, by coating the dielectric body with a colloidal suspension of graphite in water and subsequently pouring the molten alloy into contact with such coated surface.

In the drawing:

Fig. 1 is a side view partially in section of a. suspension insulator constructed in accordance with this invention; and

Fig. 2 is a similar view of a stand-oi! insulator.

Referring to the drawing in detail, an insulator designated generally III comprises a dielectric body which is provided with the usual skirt II and head I2, the latter being formed on its exterior with a pin hole I4, the side walls of which are formed with annular ribs which form anchorages for a suitable alloy by which metal parts are attached to the dielectric body. The dielectric body of the insulator Il is preferably formed of glass of the composition disclosed in theSullivan and Taylor Patent No. 1,304,623 issued May 27, 1919.

In assembling the glass and metal parts to form a complete insulator, the glass is preferably heated to a temperature of about 125 C. after which the exterior oi' the head and interior of the pin hole is coated as at I5 with a colloidal suspension of graphite in water commonly sold underthe trade name Aqua-Dag. After so coating the head and pin hole of the dielectric body, it is again heated to a temperature of about 330 C. after which a metal cap I6 is fitted over the head and a metal pin I'I is inserted in the pin hole and molten alloy I8 is poured into the spaces between the glass and metal parts., Due to the initial heating and subsequent reheating of the dielectric body, any moisture residing in the coating will be vaporized, thus leaving a thin film of very finely divided graphite on the surface of the glass which effectively prevents the adhesion of the alloy to the glass. The rapidity of the vaporization of the water which forms the vehicle for the graphite insures its rapid escape into the atmosphere before the alloy contacts with it and hence solid castings which conform accurately to the shape of the glass and metal parts and are free from voids or blow-holes are formed which results in uniformly high strength of the finished product.

In Fig. 2, I have illustrated an insulator of the stand-off type to which my invention is applicable. A dielectric body I9 which in the present instance, consists of a glass rod is coated adjacent opposite ends with a coating 20 of colloidal graphite suspended in water and dried as above described after which the coated ends of the glass part I9 are inserted into the sockets 2i of the metal fittings and secured in place by pouring molten alloy 22 in the spaces between the sockets and the glass.

Due to the lubricating eect of the colloid graphite no adhesion will take place between the alloy and the glass parts of insulators constructed as above described with the result that expansion and contraction of the parts may take place without danger of injuring the glass surface and weakening the insulator. Moreover, due to the lack of gassing of the graphite, solid alloy castings are formed and the maximum strength of the completed unit is assured.

While in the foregoing, there has been shown and described the preferred embodiment of my invention, it is to be understood that minor changes in the details of construction, combination and arrangement of parts may be resorted to without departing from the spirit and scope of my invention as claimed.

What I claim is:

An insulator comprising a dielectric body having a head and a pin-hole, a coating of colloidal graphite on the head and the wall of the pin-hole, a cap enclosing the head, a pin in the pin-hole and a fusible alloy filling the space between the head and the cap and the pin and pin-hole.

. CLARENCE H. DIBBLE. 

